MAINTAINERS, git-mailrc: socfpga: Change co-maintainer to Tien Fong Chee

I'm no longer work in Intel, change Intel SoCFPGA co-maintainer to
Tien Fong Chee.

Signed-off-by: Ley Foon Tan <lftan.linux@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>